Sustainable intensification through double-cropping and plant-based fertilization: production and plant-soil nitrogen interactions in a 5-year crop rotation of organic vegetables

A sustainably intensified (SI) organic vegetable rotation, employing plant-based fertilizers, more crops, reduced tillage, and cover crops was compared to common practice (CP) where plants were fertilized with animal manure, typically one crop was grown per season, soil was plowed and often left bare over winter. Second and third-year results are presented. Nitrogen (N) input obtained within the rotation from N2 fixed by legume cover crops was higher under SI (34% potential self-sufficiency) than CP (5%). Marketable yields of cabbage, celeriac, leek, lettuce, and onion were similar, and aboveground dry matter increased by 16% under SI (8.6 Mg ha−1) compared to CP (7.5 Mg ha−1). Nitrogen use efficiency (N output/ N input) was 8–16% higher under SI compared to CP, mainly due to the full year clover. Nitrogen surface balance (N input – N output) was higher for SI compared to CP, indicating increased N leaching risk under SI. Short season and shallow-rooted crops under SI left more mineral N to 2.5 m depth in autumn than deeper-rooted crops under CP. Cover crops indicated to mitigate N leaching risk. Vegetable production can be intensified sustainably using more yielding crops, cover crops, reduced tillage, and plant-based fertilizers.